Needle carrier for blindstitch machines



'Jan. 12, 1960 E. F- DUNN NEEDLE CARRIER FOR BLINDSTITCH MACHINES Filed July 17. 1957 Patented Jan. 12, 1960 NEEDLE CARRIER FOR BLINDSTITCH MACHINES Earl F. Dunn, Monroe, Conm, assignor to The Singer Manufacturing Company, Elizabeth, NJ., a corporation of New Jersey Application July 17, 1957, Serial No. 672,418

Claims. (Cl. 112-176) This invention relates to sewing machine needle clamps, and more particularly, to a needle clamping device for the curved needle of a blindstitch sewing machine or the like.

It is a function of a blindstitch sewing machine to produce stitches between two or more plies of fabric in such a manner that the threads of the stitching are not visible on the face ply of the fabrics. One of the most conventional forms of blindstitch sewing machine construction is that illustrated in the accompanying drawings in which a curved needle is employed, preferably being bent in an arc of a circle and supported on the machine for movement in an arcuate path substantially coincident with its curved shape. A bight or ridge is formed in the work fabrics with the face ply innermost and the ridge is presented in the path of the needle. The needle will thus pass into and out of the same side of the work on which side all of the sewing threads will be concatenated thus not being visible on the face ply after the work fabric has been stitched.

A needle is inherently slender in shape and must be tempered so as to flex rather than break in absorbing the many and varied forces to which it is subjected. The machine parts with which the needle cooperates or engages during operation can be designed so as to effect a minimum or in any event a predetermined deflection of the needle. There are, however, other factors which can cause deflection of the needle over which the machine designer has no control. One such factor is the nature and finish of the work fabrics. A soft fabric may cause little or no deflection of the needle, While a hard tightly woven fabric, a fabric with tough wiry fibers, or a loaded or sized fabric frequently can cause the needle point to glance as it strikes the fabric, thus deflecting the needle from its normal path of travel. In a blindstitch sewing machine deflection of the needle due to glancing as the needle strikes the fabric is highly objectionable. If the needle is adjusted so as to penetrate only halfway through the face ply of fabric, thus giving the maximum strength of scam commensurate with the seam being invisible on the face ply of fabric, a very slight deflection of the needle in one direction will cause the needle to miss the face ply completely, thus making a poor and weak seam, while a slight deflection in the other direction can cause the needle to penetrate the face ply completely, thus exposing the seam to view from the face ply and spoiling the appearance of the article.

It is an object of this invention to provide a needle carrier for a curved sewing machine needle which provides the machine operator with a means for minimizing objectionable deflection of the needle caused by the characteristics of the Work fabrics being stitched.

This invention thus has utility in blindstitch sewing machines employing a curved needle, however, the invention is not limited to use with a blindstitch sewing machine but will prove advantageous with any sewing machine of the curved needle variety.

More specifically, it is an object of this invention to provide a means available to the sewing machine operator for regulating the angle of incidence of a curved needle with respect to the work fabric to be penetrated by the needle without disturbing the timing of the needle or the stitching point, i.e., the point on the fabric at which needle penetration occurs.

With the above and additional objects and advantages in view as will hereinafter appear, this invention comprises the devices, combinations, and arrangements of parts hereinafter described and illustrated in the accompanying drawing in which:

Fig. 1 represents a front elevational view of the sewing head and work-supporting arm portions of a blindstitch sewing machine in which the stationary presser plate is illustrated in vertical cross section taken substantially in the vertical plane of the needle axis,

Fig. 2 represents an enlarged view of the needle and needle carrier and includes an illustration of fabric plies positioned by the ridge former for penetration by the needle, and

Fig. 3 represents a cross sectional view of the needle carrier taken substantially along line 33 of Fig. 2.

The blindstitch sewing machine of which portions are illustrated in Fig. l is of the type disclosed in greater detail in the United States patent of Parry, No. 2,678,619, May 18, 1954, to which reference may be had for those aspects not directly concerned with the needle carrier. For purposes of understanding the present invention, the sewing machine includes a work-supporting table 11 in which is carried an oscillatory ridge former 12 over which the plies of fabric to be stitched are placed face down. As illustrated in Fig. 2, the face or outer ply of fabric and a lining or hem fold ply 1 are shown in position on the ridge former.

overhanging the work table, the machine is provided with a stationary bracket arm 13 to which is attached a presser plate 14 which, as illustrated in Fig. 1, is provided with an aperture 15 upwardly through which the ridge former forces a bight or ridge in the fabrics to be stitched. The presser plate 14 is also formed with an arcuate upwardly open slot 16 which provides a channel in which the blade of a curved needle 17 moves. The needle cooperates with a looper 18 carried in the bracket arm 13 to form single thread chain stitches in the up thrust ridges of fabrics formed on the ridge former. It will be understood that the position of the work table and of the ridge former may be controlled very accurately by known means which do not form a part of this invention so that the degree of penetration of the needle into the ridge of fabric may be regulated with great nicety.

The needle is gripped between the two parts 19 and 20 of a needle clamp by means of a clamp screw 21. Part 20 of the needle clamp is formed with an arcuate sided tang 22, the center of curvature of the sides of the tang being formed to occur at the point of the needle when it is properly fixed in the needle clamp. Formed in the tang is an arcuate slot 23 having a similar center of curvature occurring at the needle point. As illustrated in Fig. 2 the tang and the slot in the tang are formed symmetrically at a radius R having its center at the needle point. Carried in the bracket arm 13 is an oscillatory needle drive shaft 24 to the free extremity of which is fixed a rock arm 25 by means of a split collar 26 and a clamp screw 27. The rock arm is formed with a seat in the form of an arcuate slot 28 with arcuate side walls corresponding in curvature to the sides of the tang 22. The tang is slidably received in the seat 28 of the rock arm and a clamp screw 29 threaded into the rock arm extends through the tang slot 23 to secure the tang in selected position of adjustment within a range of positions on the rock arm as limited by the length of the tang slot 23.

Since the radius of curvature of the rock arm seat 28 and the tang 22 has its center at the point of the needle, adjustment of the tang along the seat 28 will not affect the timing of the needle stroke nor will it affect the point of first contact of the needle with the fabrics. Adjustment of the tang 22 in the seat will influence only the angle at which the needle strikes the work which may be termed the angle of incidence of the needle. By angle of incidence is meant the angular arrangement of a line tangent to the curved needle at the needle point with respect to a line perpendicular to the point of first contact of the needle with the fabrics. The needle is conventionally positioned such that the arcuate ccnterline of the needle blade corresponds to the path of movement of the needle. I11 Fig. 2 this conventional position is indicated by the dot and dashed line A and is the position in which the parts are illustrated in Fig. 2. in the event that the characteristics of the fabric are such that the needle point is being deflected upwardly as might be the case if a hard finished fabric were being stitched, the needle will penetrate less of the face ply f of the fabrics. The operator would notice such a condition by the fact that the sewing threads would not hold the face ply sccurely and might periodically fail to engage the face ply at all. This condition can be remedied with the present invention by simply loosening the clamp screw 29 and shifting the tang 22 deeper into the seat 28 so that the centerline of the needle will occur along a line such as line B in Fig. 2. The angle of incidence would thus be made steeper and the tendency for the needle to deflect upwardly would be minimized.

Similarly, if a soft fabric is being stitched or a fabric with a high nap, the needle point may catch more quickly into the fabric and be deflected downwardly thereby penetrating too deeply into the face ply of fabric. In such a case the tang 22 can be adjusted farther out of the seat 28 so as to position the needle centerline along a line such as line C in Fig. 2 in which the angle of incidence has been made more acute.

When the needle has been adjusted out of the conventional position as indicated by the line A in Fig. 2, all points along the needle blade will not travel along the line A and the position of the needle blade in the fabrics will shift slightly toward and away from the ridge former. This slight shifting, however, has not been found to be objectionable with most fabrics, primarily because it occurs after penetration has occurred and therefore, after the relationship of the needle to the fabric has been established. The flexibility of the needle and the inherent ability of most woven fabrics to stretch slightly provides for ready compensation for the slight misalignment of the needle with its path of movement. The important criterion of consistent stitching is the path that the point of the needle takes as it passes through the fabrics, once that has occurred the remainder of the needle blade will follow that course despite slight misalignments.

When blindstitching must be applied to certain very soft or weak fibered fabrics, at misalignment of the armate portion of the needle blade with its arcnate path of movement may not be compensated for by the flexibility of the needle and fabrics. Particularly in the position B as illustrated in Fig. 2, wherein the needle would tend to shift away from the ridge former as needle penetration progressed, the sewing thread may be torn out of the fabrics. In the present invention, such a condition can be alleviated quickly and easily by simply changing the angle of incidence of the needle toward position A or C as illustrated in Fig. 2 until the tearing out of the stitches no longer occurs.

The present invention provides a simple arrangement whereby in the stitching of fabrics of any particular characteristics the machine may be readied rapidly and easily to produce consistent accurately controlled stitches. The readying of the machine for sewing on any particular fabric by means of this invention requires but a single adjustment since the control means of this invention for varying the angle of incidence of the needle disturbs neither the needle timing nor the stitching point.

Having thus described the nature of the invention, what i claim herein is:

i. In a sewing machine having a work-supporting member and an oscillatory needle-driving shaft spaced from said worlosupporting member, a curved pointed needle, means for securing said needle to said needledri ing shaft with said needle point disposed in a predetermined position relative to said work-supporting member. and means associated with said needle securing means for selectively varying the angle of incidence of said needle with respect to said work supporting member without disturbing said predetermined position of said needle point.

2. in a sewing machine having a curved pointed needle. a needle-actuating shaft. and a needle-driving rock arm fixed on said shaft, clamp means effective to secure said needle to said rock arm with the axis of said needle disposed in a predetermined plane and with the needle point disposed in a predetermined position relatively to said rock arm, and means associated with said clamp means for selectively varying the angular arrangement of said needle with respect to said needle-driving rock arm about said predetermined position of the needle point and with the axis of said needle remaining within said predetermined plane.

3. In a sewing machine having a needle with a curved blade and a pointed free extremity, a needle-actuating shaft, and a needle-driving rock arm carried on said shaft, a needle-clamp member formed with a needle accommodating seat, means to secure said needle in said seat, and interengaging fastening means on said needle-clamp member and on said needledriving rock arm effective to secure said needle blade in any one of a range of angular positions relative to said needledriving rock arm with the pointed free extremity of said needle occupying a fixed predetermined position relatively to said needle-driving rock arm throughout the entire range of needle blade positions.

4. In a sewing machine having a needle with a curved blade and a pointed free extremity, a needle-actuating shaft, and a needle-driving rock arm fast on said shaft, a needle-clamp member formed with a needle-accommodating seat, means to secure said needle in said seat, interengaging means on said needle-driving rock arm and said needle-clamp member confining said needleclamp member to sliding movement with respect to said needle-driving rock arm in an arcuate path about a center substantially coincident with the pointed free extremity of said needle secured in said seat, and means for securing said needle-clamp member with respect to said needle-driving rock arm in selected position along said arcuate path.

5. In a sewing machine having a needle with a curved blade and a pointed free extremity, a needle-actuating shaft, and a needle-driving rock arm fast on said shaft, a needle-clamp member formed with a needle-accommodating seat, means to secure said needle in said seat, a tang formed on said needle-clamp member having arcuate sidewalls of which the center of curvature is substantially coincident with the pointed free extremity of said needle secured in said seat, said needle-driving rock arm being formed with an arcuate slot having a radius of curvature equal to that of said tang sidewalls, and means for securing said tang in selected position in said slot.

References Cited in the file of this patent UNITED STATES PATENTS 1,069,010 Hemleb July 29, 1913 1,604,710 Mueller Oct. 26, 1926 2,248,439 Scheibel July 8, 1941 

